This application relates to a method of synthesising a feedback signal of an excitation voltage for a sensor.
Control systems are becoming increasingly complex when utilized with modern mechanical systems. In one type of control system, there are a plurality of sensors sensing the position of various components within a mechanical system. As an example, one type sensor may monitor a linear position of an actuator driving a mechanical component. A second sensor may sense a position of a valve for providing hydraulic fluid to drive the actuator.
There are many types of sensors available. It is known to have simpler sensors and more complex sensors. There are relatively complex sensors known as 5-wire Linear Variable Differential Transformer (LVDT) and Rotary Variable Differential Transformer (RVDT) sensors, which may be utilized for more critical sensing applications. These 5-wire LVDT and RVDT sensors have enhanced feedback of the reliability of their sensing. As an example, they have increased validity due to a constant sum check. There is no need to monitor the voltage excitation sent to a 5-wire sensor, as the sensed position can be determined based solely on the sensor outputs making the reliability and accuracy of the position measurement independent of the exact value of the excitation input to the sensor. However, the 5-wire sensors are relatively expensive and large, and require greater computing power at a related control.
On the other hand, there are less sophisticated sensors known as 4-wire Linear Variable Differential Transformer (LVDT) and Rotary Variable Differential Transformer (RVDT) sensors. These do not provide a sum check, and the feedback provided by such sensors typically needs to be adjusted ratio-metrically such that a sensor excitation based weighting factor can be applied to the sensed position feedback. On the other hand, the 4-wire LVDT and RVDT devices are relatively small and inexpensive compared to the 5-wire devices.
The 4-wire LVDT and RVDT devices require feedback of an excitation voltage to determine the weighting factor, and in the past if that feedback has failed, the 4-wire sensor could not be determined to be accurate or reliable.